Conformational study of a guaiacyl beta-O-4 lignin model compound by NMR. Examination of intramolecular hydrogen bonding interactions and conformational flexibility in solution
Copyright 2004 John Wiley & Sons, Ltd.
| Veröffentlicht in: | Magnetic resonance in chemistry : MRC. - 1985. - 42(2004), 3 vom: 27. März, Seite 337-47 |
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| 1. Verfasser: | |
| Weitere Verfasser: | , , , |
| Format: | Aufsatz |
| Sprache: | English |
| Veröffentlicht: |
2004
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| Zugriff auf das übergeordnete Werk: | Magnetic resonance in chemistry : MRC |
| Schlagworte: | Journal Article Research Support, Non-U.S. Gov't Indicators and Reagents Protons Hydroxyl Radical 3352-57-6 Guaifenesin 495W7451VQ guaiacylglycerol-beta-guaiacyl ether 7382-59-4 mehr... |
| Zusammenfassung: | Copyright 2004 John Wiley & Sons, Ltd. Intramolecular H-bonding interactions were investigated in solution for the threo and erythro diastereomeric forms of a guaiacyl beta-O-4 lignin model compound by using the NMR data obtained from hydroxyl protons. Temperature coefficients of the chemical shifts (ddelta/dT) and coupling constants (3J(HCOH)) were measured in aprotic and protic solutions: DMSO-d6, acetone-d6 and acetone-d6-water. The NMR parameters do not support the existence of strong and persistent intramolecular H-bonds that could participate in the stabilization of the guaiacyl beta-O-4 structure in solution, but instead indicate that intermolecular H-bonds to solvent predominate. 1D NOE experiments nevertheless revealed the presence of a direct chemical exchange between the hydroxyl protons, suggesting the possible existence of weak and transient intramolecular H-bonding interactions. The conformational flexibility of the threo structure was also investigated in acetone solution from the measurement of long-range 1H, 1H and 1H, 13C coupling constants and from NOESY experiments. The NMR data are not consistent with any single conformation, indicating that different conformers co-exist in solution. The experimental results support the conformational flexibility predicted by molecular dynamics simulations performed in a previous study. Finally, both experimental and theoretical approaches indicate that weak intramolecular H-bonds can exist transiently in solution, breaking and reforming as the beta-O-4 molecule undergoes conformational interconversion, but cannot be invoked as possible means of conferring rigidity to the beta-O-4 structure |
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| Beschreibung: | Date Completed 04.04.2005 Date Revised 21.11.2013 published: Print Citation Status MEDLINE |
| ISSN: | 0749-1581 |